The objective of this research is to do extensive psychophysical analysis of the visual characteristics of patients with retinal diseases. Certain retinal diseases are known to affect the blue cone mechanism first. Thus, the Stiles-Crawford effect, pigment kinetics, Westheimer functional relations, area summation, transient Stiles-Crawford effect, spatial and temporal characteristics will be used to make inferences regarding the relative role of receptors and neural organization affecting the blue cone mechanism specifically in patients with early retinitis pigmentosa.